Problem: Simplify the following expression: $y = \dfrac{9}{8x} - \dfrac{1}{3x}$
In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $8x$ and $3x$ $\lcm(8x, 3x) = 24x$ $ y = \dfrac{3}{3} \cdot \dfrac{9}{8x} - \dfrac{8}{8} \cdot \dfrac{1}{3x} $ $y = \dfrac{27}{24x} - \dfrac{8}{24x}$ $y = \dfrac{27 -8}{24x}$ $y = \dfrac{19}{24x}$